We moderators were contacted by a StackExchange community moderator about this:

Last year, on our Gaming site, we hosted an event called Hat Dash, where users earned "hats" for their gravatars by completing certain tasks (analogous to badges). Certain actions would trigger the user receiving a hat, which their gravatar could then "wear".

For example, editing a post would yield an editor-themed hat (fedora with pen) to the editor.

This year, we're expanding the promotion to all sites which choose to participate, and redesigning the hat selection to be more appropriate to the entire network (no severed Wampa heads). Some of it is holiday-themed, some of it is a bit silly, and all of it is (hopefully) fun!

This event will run from 19 December 2012 to 4 January 2013. Users will be able to see their entire hat collection on http://winterba.sh. That site will also have a landing page, explaining the rules and other details of the event.

Individual users who don’t want to participate, don’t want to see hats, and/or are generally anti-hat will have an "I hate hats" option available, just as we had on Gaming last year.

The only visual change to the site itself will be the presence of the hats and the "I hate hats" button in the footer.

All responses will need to be in by 28 November 2012. Sites that haven’t responded by then will be considered to have "opted out" from the event.

I propose we do a little voting thing. If votes are 50:50, I'll decide. (I am PRO) ;-).